A timeline of the development & history of
telephone switching systems from the past to the present
Development & History Timeline
1876 - Alexander Graham Bell files
patent on the modern telephone
1891 - Step-by-Step
(Strowger) Switch was patented by Almon Strowger
1892 - First commercial Step-by-Step
switch exchange opens in La Porte, IN on November 3rd. The system is provided by the Automatic Electric Company under Strowger patents.
1919 - November 8th, the first Step by Step switch was installed in the Bell system (not inherited due to
purchase of telephone companies with existing switches) is brought into service in Norfolk, VA. This exchange is installed by the Automatic Electric Company of Chicago for the Bell System.
1920 - First Western Electric Panel
switch installed in Omaha, NE.
1921 - On July 30, the first Step-by-Step
switch made by Western Electric is installed in Dallas.
1928 - On May 27th, the first 350A Community
Dial Office in the Bell System is opened in Arcadia, California.
1938 - The first #1
switch is installed at the Troy Avenue central office in Brooklyn, NY.
1941 - First installation of
Crossbar Tandem (XBT) regional tandem switch.
1943 - The first #4
toll tandem switch was installed in Philadelphia, PA.
1948 - On July 11th, the first #5
switch was installed at Media, PA.
1951 - The first 356A Community Dial Office (75 lines) is installed in Roberts, Idaho on February 15th.
1951 - On November 10, the trial of
customer-dialed DDD (Direct Distance Dialing) begins at Englewood, N.J.
1953 - Western Electric develops the
Card Translation System for the #4 Crossbar toll tandem switch.
1955 - On March 18th, AT&T marks the announcement of the initial trial installation of electronic switching for
1956 - First installation of North
Electric NX-1 Crossbar switch in Seymour, IN.
1960 - November 1st sees the first
field trial of Touch Tone calling undertaken in Findlay, OH. (#5
1960 - On November 17th, AT&T
conducts customer trials begin of the world's first electronic
telephone switch in Morris, IL utilizing cold-cathode vacuum
1963 - AT&T introduces
commercial use of Touch Tone service in Carnegie and Greensburg, PA
(Modified #5 Crossbar).
1965 - On May 30th, Western Electric
installs the first #1ESS electronic telephone switching system is installed in Succasunna,
NJ. Initially, only 200 of the 4,300 subscribers take advantage of the new Custom Calling Services such as third-way calling & speed dialing.
The #1ESS is transistor based and is used as a local metropolitan
switch allowing for 65,000 lines and 16,000 trunks.
1966 - On June 15th, AT&T demonstrates first International Direct Distance
Dialing (IDDD) utilizing 10 digits on a modified #5 Crossbar switch (no other #5 Crossbar switches were used for IDDD).
1968 - The #1ESS is modified for use
as both a local metropolitan switch and local tandem switch.
1969 - Western Electric introduces Electronic Translator System (ETS)
for #4 Crossbar
toll tandem switches.
1970 - March 1st sees the introduction of international DDD from London to New York
City (#1ESS switch with modified #4 Crossbar switch that served as
1970 - Western Electric develops
the #2ESS switch for local suburban has 30,000 lines and trunks together.
1972 - Automatic Electric introduces
electronic switching system. Last installation of Western
Electric #5 Crossbar
switch in Spencer, OK.
1974 - The #1ESS is adapted to allow 2-wire toll switching.
1976 - AT&T installs its first
#4ESS full digital toll tandem switch in Chicago, IL as a large 4-wire toll
tandem for use of 100,000 trunks. Last installation of #4 Crossbar
toll tandem switch.
1976 - The 1A processor is
introduced, upgrading the #1ESS
switch to #1AESS for large metropolitan local use has 90,000 lines and 32,000
1976 - Northern Telecom (Nortel)
demonstrates the DMS-10
at the Digital World expo in February.
1976 - Vidar
(later TRW-Vidar) demonstrates their ITS-5 local central office
1976 - Western Electric develops the
#2BESS for local suburban use has 30,000 lines and trunks together.
1976 - Western Electric develops the
#3ESS for local rural use has 5,800 lines and trunks together.
1977 - Stromberg-Carlson conducts
field trial and installation of first production switch of their Digital
Central Office (DCO) in Richmond Hill, GA.
1977 - Siemens of Germany begins
development of their EWSD
1977 - First production Northern
installed in Fort White, FL in October.
1977 - The #1AESS is adapted for using 4-wire toll.
1978 - Vidar
installs first commercial production ITS-4/5 switch.
1978 - Automatic Electric develops
the GTD-3 (#3EAX) full digital local office switch.
1979 - Western Electric develops the
#10A RSS (remote switching system) for local small rural areas with 2,000 lines.
1979 - The #1AESS is adapted for local, tandem, and toll capability.
1979 - Northern Telecom installs
first production DMS-100
local central office switch.
1982 - Western Electric installs
the first #5ESS local central office switch for local rural to large metropolitan areas with tandem and toll capabilities has from 150,000 lines and 50,000 trunks to 0
lines and 60,000 trunks.
1982 - Automatic Electric develops
(#5EAX) digital local office switch.
1984 - Court ordered divestiture
breaks up AT&T. Local operating companies form seven Regional Bell
Operating Companies (RBOCs). Western Electric/Bell Labs is absorbed
1989 - Automatic Electric &
AT&T join forces to form AGCS.
1990 - The telephone switch division
of Stromberg-Carlson is sold to Siemens.
1996 - AT&T spins off hardware
technology development into Lucent
Technologies. AGCS becomes part of Lucent.
1999 - Lucent installs last #4ESS
switch in Atlanta, GA. A total of 145 #4ESS machines were installed in
the AT&T Long Lines network with several more installed for
regional (RBOC) use.
2002 - Last known Step-by-Step
switch in North American public switched network is replaced with a
digital (DMS-10) switch in Nantes, QC Canada. This switch was probably
the last fully electro-mechanical switch in the North American PSTN.
2003 - Sprint Local (EMBARQ)
begins replacement of traditional Nortel DMS-100 digital time-domain
circuit-switched telephone switches with new Nortel Communications
2005 - Last known group of Vidar
switches in the US are replaced with CopperCom
in Linn Grove, Peterson and Rembrandt, IA.
2005 - AT&T merges with SBC
(former Southwestern Bell Company, an RBOC spun off from AT&T in
1984) to form "the new at&t".
2006 - The local landline divison
of Sprint is spun off as EMBARQ.
2006 - BellSouth merges with the
"new at&t". BellSouth was the last "Baby Bell" to keep its original
name from the 1984 breakup of the old AT&T.
2006 - Lucent is sold to French
telephone equipment maker Alcatel to form
2006 - Windstream is formed from
Valor telecom and the former wireline division of Alltel.
2007 - With all of Cingular under
one owner, the name is changed to at&t Mobility.
2009 - EMBARQ and CenturyTel merge
2009 - Centennial Wireless merges
with at&t Mobility
2009 - Alltel Wireless merges with
2010 - CenturyLink buys Qwest and
becomes largest PSTN company in terms of square mileage.
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Page last modified January 11, 2013
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